Amplifying device and wireless transmission device using the same

Abstract

An amplifying device 1 of the present invention performs distortion compensation on distortion appearing in input-output characteristics of an amplifier 4 based on an input signal and an output signal of the amplifier 4 , and includes a predistorter 23 that obtains the input signal and the output signal and performs distortion compensation of the amplifier; an ACLR calculation unit 25 that detects the distortion level of the distortion of the amplifier 4 ; and an adjustment unit 26 that adjusts the power of the input signal in accordance with the distortion level.

The invention claimed is: 
     
       1. An amplifying device comprising:
 an amplifier that amplifies a power of an input signal; 
 a predistorter that obtains the input signal and an output signal outputted by the amplifier in response to the input signal and that performs distortion compensation of the amplifier; 
 a distortion level detection unit that detects a distortion level of distortion that appears in input-output characteristics of the amplifier for which characteristics the distortion compensation has been performed; and 
 an adjustment unit that adjusts the power of the input signal in accordance with the distortion level, wherein 
 the adjustment unit indirectly adjusts the power of the input signal by adjusting the power of the output signal to be obtained by the predistorter. 
 
     
     
       2. The amplifying device according to  claim 1 , wherein
 the adjustment unit determines whether the distortion level detected by the distortion level detection unit is greater than a first threshold value predetermined as an upper limit value that is allowable as the distortion level, and when determining that the distortion level is greater than the first threshold value, the adjustment unit performs the adjustment so as to decrease the power of the input signal. 
 
     
     
       3. The amplifying device according to  claim 2 , wherein
 the adjustment unit determines whether the distortion level is lower than a second threshold value which is set to a value smaller than the first threshold value, and when determining that the distortion level is lower than the second threshold value, the adjustment unit performs the adjustment so as to increase the power of the input signal. 
 
     
     
       4. The amplifying device according to  claim 3 , wherein
 an amount of change used when the adjustment unit increases the power of the input signal is set to a value smaller than an amount of change used when the adjustment unit decreases the power of the input signal. 
 
     
     
       5. The amplifying device according  claim 1 , wherein
 after adjusting the power of the input signal, the adjustment unit waits for a predetermined time period to elapse, before adjusting the power of the input signal again. 
 
     
     
       6. The amplifying device according  claim 1 , wherein
 the adjustment unit adjusts the amount of change for the power adjustment of the input signal, in accordance with the power of the input signal. 
 
     
     
       7. The amplifying device according to  claim 6 , wherein
 the adjustment unit performs the adjustment in accordance with a maximum power value of the input signal. 
 
     
     
       8. The amplifying device according to  claim 1 , wherein
 the adjustment unit adjusts the amount of change for the power adjustment of the input signal, in accordance with the distortion level. 
 
     
     
       9. The amplifying device according to  claim 1 , wherein
 the distortion level detection unit obtains an output signal from the amplifier, determines a leakage power ratio of a power of an adjacent frequency band adjacent to an available frequency band, which is available for the output signal, to a power of the available frequency band, and outputs the leakage power ratio as the distortion level. 
 
     
     
       10. An amplifying device comprising:
 an amplifier that amplifies a power of an input signal; 
 a predistorter that obtains the input signal and an output signal outputted by the amplifier in response to the input signal and that performs distortion compensation of the amplifier; 
 a distortion level detection unit that detects a distortion level of distortion that appears in input-output characteristics of the amplifier for which characteristics the distortion compensation has been performed; and 
 an adjustment unit that adjusts the power of the input signal in accordance with the distortion level 
 wherein 
 the predistorter estimates a model representing the input-output characteristics of the amplifier by using the input signal and the output signal, and performs the distortion compensation of the amplifier by using the model, and 
 the distortion level detection unit determines, as an amount of modeling error, a difference between the model estimated by the predistorter and the input-output characteristics of the amplifier expressed based on the input signal and the output signal, and outputs the amount of modeling error as the distortion level. 
 
     
     
       11. The amplifying device according to  claim 1 , wherein the adjustment unit directly adjusts the power of the input signal. 
     
     
       12. A wireless transmission device including an amplifying device, wherein
 the amplifying device is the amplifying device according to  claim 1 .